PROPERTIES High compressive strength Lower tensile strength Negligible change when temp changes Develops cracks over time

2. High compressive strength
Lower tensile strength
Negligible change when temp changes
Develops cracks over time

3. Cement
Water
AggregatesReinforcement
Admixtures

4.  Used in mixing and curing.
 Potable water should be used.
 Sea water is not permitted.
 pH value of water should not be less than 6.
Disadvantages of using more water and
advantages of using less water

5. Disadvantages of using
more water
 Creates a diluted
paste.
 Excess water bleeds
out onto the surface.
 This affects the
compressive and
tensile strengths.
 Loss of cohesiveness
and homogeneity.
 Harmful to strength
and durability.
Advantages of using
less water
 Increased strength.
 Lower permeability.
 Increased resistance to
weathering.
 Better bond between
concrete and
reinforcement.
 Reduced shrinkage
and cracking.
 Less volume change
from wetting and
drying.

6. FINE AGGREGATE COARSE AGGREGATE
 Size more than 4.75mm.
 Includes gravels and
crushed stones.
 Obtained by crushing
various types of
granites, hard lime
stones and sand stones.
 Harsh concrete.
 Size less than 4.75mm.
 Includes natural sand or
crushed stone with
most particles passing
through a sieve.
 Obtained from pits,
lake, river or sea-shore.
 Thoroughly washed
before use.

7.  Reinforced concrete is a composite material in
which concrete's relatively low tensile
strength and ductility are counteracted by the
inclusion of reinforcement having higher tensile
strength and/or ductility.
 . Reinforced concrete may also be permanently stressed
(in compression), so as to improve the behaviour of the
final structure under working loads. In the United
States, the most common methods of doing this are
known as pre-tensioning and post-tensioning.

8. For a strong, ductile and durable construction the
reinforcement needs to have the following properties at
least:
High relative strength.
High toleration of tensile strain.
Good bond to the concrete, irrespective of pH, moisture,
and similar factors.
Thermal compatibility, not causing unacceptable stresses
in response to changing temperatures.
Durability in the concrete environment, irrespective of
corrosion or sustained stress.

9. Two physical characteristics give reinforced concrete its
special properties:
 The coefficient of thermal expansion of concrete is
similar to that of steel, eliminating large internal
stresses due to differences in thermal expansion or
contraction.
 When the cement paste within the concrete hardens,
this conforms to the surface details of the steel,
permitting any stress to be transmitted efficiently
between the different materials. Usually steel bars are
roughened or corrugated to further improve
the bond or cohesion between the concrete and steel

10. Common failure modes of steel reinforced concrete:
Mechanical failure
Carbonation
Chlorides
Alkali silica reaction
Conversion of high alumina cement
Sulphates

12. 12
Production, Composition
&
Types

13. 13

14. 1. Acquisition of raw materials.
2. Preparation of raw materials.
3. Burning.
4. Addition of Gypsum and Distribution.
14

15. 15

16.  General Purpose
 Ordinary Portland Cement
 Sulphate Resisting Cement
High Early Strength
Low Heat Cement
Air Entraining Cement
White Cement
16

17.  Variety of artificial cement.
On hardening , its color resembles to the
rocks near Portland in England.
Main constituents : Lime , Silica , Alumina.
17

18. Lime 63%
Silica 22%
Alumina 06%
Iron Oxide 03%
Gypsum 01-04%
18

19.  Lime : Sufficient quantity forms di-
calcium silicate and tri-calcium silicate.
 Silica : Gives strength.
 Alumina : Sets cement quickly ; lowers
clinkering temperature.
19

20.  Iron Oxide : gives color to cement.
 Magnesia : helps in giving color to cement.
 Gypsum : added to increase the setting of
the cement.
20

21.  Modified form of O.P.C.
Used when O.P.C. is liable to
disintergrate.
 Uses : Hydraulic structures , canals.
21

22.  Provides strength at early stage.
 Reason : finer grinding , burning at high
temperature , increased lime content.
 Strength by Rapid Hardening Cement in 4
days = strength by O.P.C. in 14 days.
 Uses : Highway Slabs.
Suitable in Cold weather areas.
22

23.  Heat of hydration is reduced by tri-
calcium aluminate.
 Less % of Lime.
 Uses : Mass Concrete Works : Damns.
23

24.  Produced by grinding minute air
entraining materials with clinker.
 Improves workability , durability.
 Uses : Natural raisins , fats , oils.
24

25.  Keeps the content of Iron Oxide as low as
possible.
 Costlier than O.P.C.
 Uses : Architectural finishing in buildings.
25

26.  Proportion of sand and cement decides the
strength of mortar.
 Richer mixture than 1:3 proportion is prone
to shrinkage.
 When water is added to initiate the cement
and sand mixture , hydration starts and binds
sand particle and surface of masonry and
concrete.
26

27. ADVANTAGES
 Strong.
 Creates large structures
easily.
 Has high thermal mass.
DISADVANTAGES
 Subjected to cracking.
 Difficult to provide
idoneous curing
conditions.
 Not ideal when
settlement is expected.
27

29. CONCRETE MIXTURES:
Concrete admixtures are used to improve the behavior of
concrete under a variety of conditions.
There are two main types of Admixtures:
1. Chemical admixture
2. Mineral admixture

30. CHEMICAL ADMIXTUES:
reduce the cost of construction,
 modify properties of hardened concrete,
used to improve the quality of concrete during mixing,
transporting, placement and curing.

31. They fall into the following categories:
Air entrainers
Water reducers
Set retarders
Set accelerators
Super plasticizers
Specialty admixtures: which include corrosion inhibitors, shrinkage control, alkali-
silica reactivity inhibitors, and coloring.

32. MINERAL ADMIXTURES:
Mineral admixtures affect the nature of the hardened
concrete through hydraulic or Pozzolanic activity.
Pozzolans are cementations materials and include natural
Pozzolans (such as the volcanic ash used in Roman concrete),
fly ash and silica fume.
They can be used with Portland cement, or blended cement
either individually or in combinations.

33. Properties of mineral admixtures:
make mixtures more economical,
reduce permeability,
increase strength,
influence other concrete properties

34. CONCLUSIONS:
Plasticizers, super plasticizers , & Air-entraining
admixtures is mostly used.
Super plasticizers is widely used all over the world .
India is catching up with the use of super plasticizer in
the construction of high rise buildings, long span
brides because it reduced cement content, increased
workability, & increased strength.